1. Field of the Invention
The present invention is directed to a read-out system for a luminescent storage screen, of the type suitable for use in an x-ray diagnostics installation for retrieving a latent image stored in the screen.
2. Description of the Prior Art
Read-out systems are generally known for use in x-ray diagnostics installation for retrieving an image which is latently stored in the screen. In such known systems, the luminescent storage screen is planarly scanned pixel-by-pixel with a deflected scan beam of a first wavelength in order to retrieve the image, the scan beam causing the storage screen to luminesce and generate light of a second wavelength. The light is detected by a detector system which includes a light conductor which conducts the light of the second wavelength onto a light detector.
Such a read-out system is disclosed in European Application 0 363 522, wherein a tubular light conductor having mirrored interior walls is disposed over the luminescent storage screen. The tubular light conductor has a slot-shaped passage through which the scan beam, which is generated by a radiation source and is deflected for scanning, can pass so that a complete line of the luminescent storage screen can be scanned and excited. Due to the excitation, the luminescent storage screen emits light pixel-by-pixel, this light being reflected by the walls of the tubular light conductor and being conducted onto light detectors attached to one side wall of the tubular light conductor. These light detectors generate an electrical signal corresponding to the brightness of the light emitted by each pixel of the luminescent storage screen.
In such a light conductor, however, it is a problem that not only the light emitted by the luminescent storage screen (i.e., the useful signal) passes through the entry opening of the light conductor, but also the light of the scan beam, reflected at the surface of the luminescent storage screen, proceeds into the light conductor as an unwanted signal, and can emerge within the light conductor at a different location due to reflections. The intensity of this reflected light of the first wavelength is considerably stronger than that of the emitted light of the second wavelength. The reflected light may also excite pixels lying at a greater distance within the scan line, so that a constant premature read-out of all pixels ensues, as seen in totality. This known system, therefore, includes a filter for eliminating the reflected light which is disposed in front of the detector. Although this filter prevents light of the first wavelength from reaching the light detector, the filter cannot prevent the aforementioned premature read-out.